WOW, you need to do the right thing no matter how you perceive his reaction. He looked embarrassed? Was he embarrassed from his friends that his Mom said hello or from his Mom that she finally saw his friends? You still need to be the adult and the smart one at that. Stop being afraid of your child and his reactions. As you said you have no idea why he is so angry. Ignore him when he is angry. At that time just walk away from him and give him space. It is as if his head and heart is filled with the garbage of the streets he needs time to unwind from that garbage before he can be approached. So give him that time and don’t approach him until he has softened. In all honesty it sounds like he is drunk.
And again I say this especially since he still has the ability to be embarrassed, write, write, write! Let him read your thoughts and feelings in the privacy of his own room where no one can see his reactions. He will read it as many times as he needs to. It will have more of an effect than the spoken word, without the confrontation. On his skewered mind right now he has to show rebellion and bravado, but he does not have to show anything as he reads in the privacy of his room at his own discretion.
Best wishes for a Shanah Tova, wishing you Bracha, Mazel , Koch and most importantanly tons of patience.